In the production of steel, a ferrous melt is typically produced in a suitable furnace and then tapped into a ladle where it is treated with one or more ingredients for refining or alloying purposes. It is well known to add calcium or other additives to the molten ferrous material at this point as a refining agent for oxide inclusion flotation, oxide inclusion, morphology modification, desulfurization, chemistry modification, etc. These additives are often fed in a wire which can be clad for ease of handling of the additive. Several methods of introducing the wire into the molten metal bath exist. One method uses a wire feeding apparatus and a lance. Another method uses a wire feeding apparatus and a directional conduit which feeds wire from above the bath without the use of a penetrating lance. This method is also known as surface feeding.
Previously, lances for wire feeding apparatuses were bulky, heavy, in order to be durable in a molten metal plant environment. Such systems require crane lifts and or heavy manual lifting during use and maintenance. Availability of the crane when needed to facilitate the changing of the lance can be limited. These heavy lances remain useful for multiple treatments of wire feeding as they are designed for long term durability. During this period of use of the heavy lances, slag and/or metal may become built up on the lance, often at the level where the upper surface of the slag contacts the lance during its penetration of the molten metal bath. This buildup of metal or slag which occurs and becomes larger from repeated use can unexpectedly fall off the lance such as during changing of a lance tip possibly injuring personnel or creating other safety issues. In addition, any buildup of metal or slag on the lance can prevent movement of the lance through a cover on the molten metal vessel. If this buildup on the lance itself falls off in one large piece, then a potential splash of liquid steel and slag could result in injury or property damage.
In order for heavy lances to achieve maximum durability, they often have replaceable tips as the tip tends to wear out before the main body of the lance. Several tips may be used during the useful lifetime of a single lance. Replacement of heavy lance tips are often done manually, sometimes from awkward positions for personnel. In addition, the replacement of the tips must be performed by personnel while working beneath a suspended lance. Such used lances which are configured for heavy lance tips are often covered by a buildup of slag or metal.
In surface fed wire systems, the penetration into the molten bath by the wire can be difficult if the slag is very viscous or thick. The wire can be bent or deflected by this slag layer preventing the wire from entering the molten bath and an unsuccessful wire treatment can result.
In an attempt to overcome the above-mentioned problems, the inventors have developed a lance which avoids the specified hazards while permitting the feeding of wire to the molten metal bath and achieving effective recovery.